I get the stupid Warbird down to 30% for the second freakin time and he hits me with some little glowing torpedos that knock me from 90 - 0 in `1 hit...
I have played this stupid mission over 10 times and each time the same outcome..
he hits me with some MASSIVE blast that destroys me in seconds or knocks me down so much that a simple phaser kills me...
Also, stay outside of 5 km range. Inside of 3, you're vulnerable to photonic shockwave, which slams your shields and stuns you for a potential slavo. Inside of 5 you're vulnerable to tractor beam, which pretty much guarantees you're going to take a salvo if you can't break it and run.
Being at that range also gives you roughly 5 seconds to respond to incoming torpedoes, easiest option I've found being evasive maneuvers for even more range and pick them off at leisure, brace for impact and emergency power to shields to reduce both shield and hull damage if you can't shoot down all three.
Aside from that, the standard things you should be doing anyway, like tac team to make sure the shield facing taking the hits is full.
easiest "I win" button against the torp salvo... automated turrets/point defense system. one was a specail pre-order bonus, the other coems on a Cstore ship that can be put on any ship now. since they have pretty much "no miss" accuracy its better than FAW or Cannon scatter volley against them.
Equip your Sci BOff with Tractor Beam Repulsor. When the Rom fires those torpedoes at you, hit the button and watch them all get pushed away harmlessly and destroyed. I set up a Sci BOff with Polarize Hull and Tractor Beam Repulsors and used him specifically for all the Romulan missions. They were a cakewalk. They also came in handy later for the Borg missions.
i have never had a problem with D'deridix warbird triple plasma torps, i usually hit the ship with sensor blackout sci ability, get on its side shield quadrant and blast the thing to hell as fast as possible before the effect wears off. additionally reverse polarity and hazard emitters also work if you do attack from the front.
The real issue is that it just takes some time to get used to the various ships' tactics. The higher the level the less you can rely an standard pew-pew to get the job done - you get more BOFF abilities and so do your opponents. You need to know when to use Shield Team to deal with the Hirogen sensor jams, what ships require some distance, when to remodulate against Borg, etc.
shield team is effective after the sensor blackout is in effect, before and it wont work, otherwise move about using a fresh shield quadrant or rebuff your shields or equalizing.
there is more to what cosmic is saying, each pperson has their own style of play. some like to shoot out sensor blackouts and use sheer DPS and rapid fire to get the job done, others use scorpion fighter decoys and then jam a torpedo up its tail pipe before the NPC ship can respond....